Architectural concrete and method of forming the same

ABSTRACT

A method of forming an architectural concrete structure having a desired look (i.e., color) and texture, wherein the method generally includes pouring a base concrete layer using conventional concrete. A surface concrete mixture is prepared and includes a mixture of sand and small aggregates to give the surface concrete mixture the desired color and texture for the architectural concrete structure. The base concrete layer provides strength and durability to the concrete structure, while the surface concrete layer provides the desired look and texture of the concrete surface. The surface concrete mixture preferably includes small aggregates to create a smooth and uniform texture.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

Technical Field of the Invention

The present invention relates generally to a method and finish forconcrete structures, and more specifically to a method of formingarchitectural concrete structure having customized architecturalattributes (i.e., color and texture), while at the same time exhibitingsufficient strength and durability.

Description of the Related Art

As is well known in the construction industry, concrete is a commonlyused material for the fabrication of structures. The desirability of theuse of concrete as a construction material is attributable to certaincharacteristics that concrete possesses in comparison to otherconstruction materials. Due to its durability, wear resistance and costeconomy, concrete is gaining widespread use in flooring applications. Asa result of its widespread use, there is an increasing demand forvariations in color and surface texture of the concrete such that theconcrete possesses improved aesthetics similar to more conventional andcostly flooring surfaces such as marble, stone and granite.

To meet the demand, the concrete industry has heretofore developedvarious coloring and surface finishing techniques for enhancing theaesthetics of the concrete. Exemplary finishing techniques include saltfinishing, multiple brook finish, form press finish, and exposedaggregate finish.

In relation to exposed aggregate finishes, there are two commonly usedtechniques to achieve the desired finish, i.e., integrally exposedaggregate and surface seeded exposed aggregate. Integrally exposedaggregate tends to be the more conventional of the two methods andgenerally includes washing or removal of the surface cement and finesfrom the concrete while the concrete surface is still plastic, i.e.,before full curing, such that the aggregate, normally rock or gravel, isleft exposed on the surface of the concrete. Due to the normal size ofsuch concrete aggregate being relatively large, as well as the washingprocess not being uniform in nature, the resultant concrete surfacederived by the integrally exposed aggregate method is extremely roughand gagged, thereby limiting its widespread use in flooringapplications.

Surface seeded exposed aggregate has been introduced, which subsequentto the pouring of the concrete, rock or gravel aggregate is broadcasted,i.e., seeded, over the top surface of the concrete and subsequentlytroweled into the same wherein upon curing the aggregate broadcast overthe surface adheres to the surface and is thus exposed. Various sizedaggregate can be broadcast over the surface of the concrete in thesurface seeded exposed aggregate technique, normally the aggregateincludes sheared or jagged edges such that the same can be worked intothe surface of the concrete and be adequately adhered thereto. Thus, theresultant concrete surface, although generally flatter and notpossessing as many surface irregularities as the integrally exposedaggregate surface, still possesses an extremely rough surface whichlimits its widespread use in flooring applications.

Therefore, there exists a substantial need in the art for an improvedmethod of forming an architectural concrete surface having a surfacewhich is smoother and more uniform than surfaces formed using existingtechniques.

BRIEF SUMMARY OF THE INVENTION

There is provided a method of forming an architectural concretestructure having a prescribed look (i.e., color) and texture. The methodgenerally includes pouring a base concrete layer using conventionalconcrete. A surface concrete mixture is prepared and includes a mixtureof sand and small aggregates to give the surface concrete mixture thedesired color and texture for the architectural concrete structure. Thebase concrete layer provides strength and durability to the concretestructure, while the surface concrete layer provides the desired lookand texture of the concrete surface. The surface concrete mixturepreferably includes small aggregates to create a smooth and uniformtexture.

According to one embodiment, the method includes pouring a base concretemixture in an unhydrated state to define a base concrete layer, whereinthe base concrete mixture includes large aggregate. The method furtherincludes preparing a surface concrete mixture including small aggregateand sand, wherein the small aggregate are smaller than the largeaggregate used in the base concrete mixture. The small aggregate andsand are mixed to define a prescribed color. The surface concretemixture is then poured over the base concrete layer while the baseconcrete mixture is in an unhydrated state, such that the surfaceconcrete mixture defines a surface layer.

The method may further include the step of forming a subgrade upon whichthe base concrete mixture is poured. The method may additionally includeproviding a concrete form, and pouring the base concrete mixture withinthe concrete form. The surface of the base concrete layer may be leveledprior to pouring the surface concrete mixture over the base concretelayer. The method may further include the step of floating the surfaceconcrete mixture after it is poured over the base concrete layer.

The surface concrete mixture may be finished after it is poured over thebase concrete layer. The finishing step may include grinding the surfacelayer, etching the surface layer, and/or sand-blasting the surfacelayer.

The step of preparing the surface concrete mixture may include removinglarge aggregate from the base concrete mixture to form the surfaceconcrete mixture.

The step of pouring the surface concrete mixture may includepneumatically projecting the surface concrete mixture over the baseconcrete layer.

The surface concrete mixture may be poured over the base concrete layerwithin eight hours after forming the base concrete layer.

According to another aspect of the present invention, there is providedan architectural concrete structure including a base concrete layerformed from a base concrete mixture including large aggregate, whereinthe base concrete layer defining a base surface. A surface layer isformed on the base surface, wherein the surface layer includes smallaggregate and sand. The small aggregates are smaller than the largeaggregate in the base concrete mixture, and the small aggregate and sandbeing mixed to define a prescribed color. The surface layer is formed onthe base surface while the base concrete mixture is in an unhydratedstate to allow the surface layer to bond to the base concrete layerindependent of a cold joint therebetween.

The present invention is best understood by reference to the followingdetailed description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These as well as other features of the present invention will becomemore apparent upon reference to the drawings wherein:

FIG. 1 is an upper perspective view of an embodiment of an architecturalconcrete structure formed in accordance with an embodiment of thepresent invention; and

FIG. 2 is a flowchart of one embodiment of a method of forming thearchitectural concrete surface.

Common reference numerals are used throughout the drawings and detaileddescription to indicate like elements

DETAILED DESCRIPTION OF THE INVENTION

The detailed description set forth below is intended as a description ofthe presently preferred embodiment of the invention, and is not intendedto represent the only form in which the present invention may beconstructed or utilized. The description sets forth the functions andsequences of steps for constructing and operating the invention. It isto be understood, however, that the same or equivalent functions andsequences may be accomplished by different embodiments and that they arealso intended to be encompassed within the scope of the invention.

Referring now to the drawings, wherein the showings are for purposes ofillustrating a preferred embodiment of the present invention only, andare not for purposes of limiting the same, there is shown anarchitectural concrete structure 10 having a base concrete layer 12 andan outer surface concrete layer 14. According to various aspects of thepresent invention, the base concrete layer 12 is formed fromconventional concrete, while the surface concrete layer 14 is customizedto have prescribed architectural characteristics (i.e., color, texture,etc.). In order to ensure proper bonding/adhering between the baseconcrete layer 12 and the surface concrete layer 14, the surfaceconcrete layer 14 is poured over the base concrete layer 12 while thebase concrete layer 12 is in an unhydrated, plastic state, which allowsthe surface concrete layer 14 to bond to the base concrete layer 12without a cold joint being formed therebetween.

As used herein, the term “architectural concrete structure” may be usedto refer to patios, parking lots, decks, porches, walkways, flooring,garages, sidewalks, plazas, entryways, fountains, or other surfacesformed of concrete. Along these lines, architectural concrete structuresprovide desirable strength and durability which is derived from theconcrete used to form the structure, while at the same timeincorporating artistic design elements to achieve a preferred look andtexture.

FIG. 2 is a flow chart illustrating one embodiment of a method offorming the architectural concrete structure. The method includes thestep of preparing a subgrade 16 (see FIG. 1), which includes forming thesubgrade 16 to a desired elevation and grade, and compacting thesubgrade 16 to a proper compaction standard. Furthermore, any utilities(i.e., sleeve and pipes—not shown) that must extend under thearchitectural concrete structure 10 preferably extend under the subgrade16.

The method further includes preparing and placing a form 18 on thesubgrade 16. In general, the form 18 defines at least one edge of thearchitectural concrete structure 10, and may be constructed from wood orother materials known by those skilled in the art. In the exemplaryembodiment depicted in FIG. 1, the form 18 includes two elongate members20 (i.e., wood beams) positioned on the ground 22 adjacent the subgrade16 to define a pour area for the concrete. The form 18 is preferablyarranged to create a pour area having the specific dimensions requiredfor the resultant architectural concrete structure 10. In the exemplaryembodiment, the architectural concrete structure 10 is formedabove-ground, and thus, the form 18 rests on the ground 22. However, inother embodiments, it may be desirable to form the architecturalconcrete structure 10 such that the top/exposed surface of thearchitectural concrete structure 10 is substantially flush with theground level 22. In that case, the form 18 may extend at least partiallybelow ground level to accommodate the designs of the architecturalstructure 10.

In order to increase the resultant strength of the structure 10 andreduce subsequent cracking of the same, reinforcement wire mesh or steelrebar 24 may be positioned above the subgrade 16 within the area definedby the form 18. In the exemplary embodiment, the concrete structure 10includes a plurality of rebars 24 positioned longitudinally between theform members 20. Although the exemplary embodiment only shows rebars 24arranged in a spaced, parallel arrangement, it is understood that otherembodiments may include rebars 24 arranged in a lattice framework, whichincludes rebars 24 arranged in an intersecting fashion.

In addition to preparing the pour area for the architectural concretestructure 10, as noted above, the concrete used in forming thearchitectural structure 10 is also prepared. The preparation of theconcrete may be performed before, during, or after preparation of thepour area.

The concrete used in forming the architectural concrete structure 10includes a base concrete mixture 26 and a surface concrete mixture 28.The base concrete mixture 26 preferably includes cement, sand andaggregate, including small aggregate and large aggregate. As usedherein, the term “small aggregate” will typically refer to aggregatepreferably having a mean average diameter of less than three-eighths ofone inch, while “large aggregate” will typically refer to aggregatepreferably having a mean average diameter of greater than three-eighthsof an inch. According to various embodiments, the base concrete mixture26 may be prepared in a manlier similar to conventional concrete.

Once the base concrete mixture 26 is prepared, the base concrete mixture26 is preferably poured to a depth which covers any rebar 24 orreinforcement member placed within the pour area over the subgrade 16.After the base concrete layer 12 is poured, the base concrete layer 12defines an exposed surface 30, which may be leveled after the baseconcrete mixture 26 is poured to define a generally smooth, planarsurface.

The surface concrete mixture 28 is different from the base concretemixture 26 and is used to form the exposed surface layer 14 of thearchitectural concrete structure 10. In this regard, surface concretemixture 28 may include unique additives to achieve the desired look andtexture of the architectural concrete structure 10. Along these lines,the preferred implementation of the surface concrete mixture 28 includescement, select sands and small aggregates which create the desired lookand texture of the architectural concrete structure 10. Along theselines, the sand and small aggregates mixed into the surface concretemixture 28 may correlate to the prescribed color of the architecturalstructure 10 (i.e., if the desired color of the architectural structure10 is red, then red sands and small aggregates are mixed into thesurface concrete mixture 28). The selected sands and small aggregatesmay not only relate to the desired color of the architectural structure10, but may also relate to the reflective qualities (i.e., dull orpolished) or other aesthetic characteristics of the architecturalstructure 10 known by those skilled in the art.

Once the surface concrete mixture 28 is prepared, it is poured over theexposed surface 30 of the base concrete layer 12 while the base concretemixture 26 is in an unhydrated, plastic state. According to a preferredembodiment, the surface concrete layer 14 is approximately ¼″ thick,wherein the thickness is defined as the distance between the upperexposed surface 32 of the surface concrete layer 14 and the interface ofthe surface concrete layer 14 and the base concrete layer 12. However,other embodiments may include a surface concrete layer that is more than¼″ thick or less than ¼″ thick.

According to various embodiments of the present invention, the surfaceconcrete mixture 28 is poured over the base concrete layer 12 withineight hours of forming the base concrete layer 12. Pouring the surfaceconcrete mixture 28 over the base concrete layer 12 while the baseconcrete mixture 26 remains in an unhydrated, plastic state allows thesurface concrete mixture 28 to bond to the base concrete mixture 26 andalso prevents a cold joint from forming between the two layers 12, 14.This results in a more structurally uniform and sound concretestructure.

According to one embodiment, the surface concrete mixture 28 and thebase concrete mixture 26 are formed as separate batches. As previouslynoted, the base concrete mixture 26 is formed similar to conventionalconcrete, and includes a mixture of cement, sand, large aggregate andsmall aggregate. On the other hand, the surface concrete mixture 28includes cement, sand and small aggregates, wherein the sand and smallaggregates are selectively added to the surface concrete mixture todefine the desired look and texture of the structure 10.

According to another embodiment, the surface concrete mixture 28 isformed from the same batch as the base concrete mixture 26. There may bestructural advantages associated with forming the surface concretemixture 28 from the same batch as the base concrete mixture 26, such ashaving a degree of uniformity throughout the concrete structure 10. Thesurface concrete mixture 28 may be formed from the base concrete mixturebatch by removing the large aggregates from the base concrete mixturebatch, and then optionally adding sand and other small aggregates toachieve the desired look and texture for the surface concrete mixture28.

After the surface concrete mixture 28 is poured over the base concretelayer 12, the surface concrete mixture 28 is floated to define a uniformouter surface. The surface concrete layer is then finished to reveal thecolor and texture of the surface mixture 28. For instance, the surfacelayer 14 may be ground, etched (acid etching or chemical etching), orsandblasted to reveal the color of the select sands and small aggregatesmixed into the surface mixture 28.

The novel and unique concrete structure 10, and related method offorming the same described herein, uniquely includes a two-layerconstruction including the base concrete layer 12 and the surfaceconcrete layer 14. The base concrete layer 12 provides structuralsupport to the structure 10, while the surface concrete layer 14provides aesthetic qualities to the structure 10. In this regard, thetwo-layer construction provides structural, as well as economicadvantages when compared to a structure formed completely with concretedevoid of large aggregates. Along these lines, the use of largeaggregates in the base mixture 26 strengthens the base mixture, and isalso more advantageous from a cost perspective.

Additional modifications and improvements of the present invention mayalso be apparent to those of ordinary skill in the art. Thus, theparticular combination of components and steps described and illustratedherein is intended to represent only certain embodiments of the presentinvention, and is not intended to serve as limitations of alternativedevices and methods within the spirit and scope of the invention.

What is claimed is:
 1. A method of forming architectural concrete, themethod comprising the steps of: pouring a base concrete mixture in anunhydrated state to define a base concrete layer, the base concretemixture including large aggregate; preparing a surface concrete mixtureincluding small aggregate and sand, the small aggregate being smallerthan the large aggregate used in the base concrete mixture, the smallaggregate and sand being mixed to define a prescribed color; and pouringthe surface concrete mixture over the base concrete layer while the baseconcrete mixture is in the unhydrated state, the surface concretemixture defining a surface layer.
 2. The method recited in claim 1,further comprising the step of forming a subgrade upon which the baseconcrete mixture is poured.
 3. The method recited in claim 1, furthercomprising the steps of: providing a concrete form; and pouring the baseconcrete mixture within the concrete form.
 4. The method recited inclaim 1, further comprising the step of leveling the surface of the baseconcrete layer prior to pouring the surface concrete mixture over thebase concrete layer.
 5. The method recited in claim 1, furthercomprising the step of floating the surface concrete mixture after it ispoured over the base concrete layer.
 6. The method recited in claim 1,further comprising the step of finishing the surface concrete mixtureafter it is poured over the base concrete layer.
 7. The method recitedin claim 6, wherein the finishing step includes grinding the surfacelayer.
 8. The method recited in claim 6, wherein the finishing stepincludes etching the surface layer.
 9. The method recited in claim 6,wherein the finishing step includes sand-blasting the surface layer. 10.The method recited in claim 1, wherein the preparing step includesremoving large aggregate from the base concrete mixture to form thesurface concrete mixture.
 11. The method recited in claim 1, wherein thestep of pouring the surface concrete mixture includes pneumaticallyprojecting the surface concrete mixture over the base concrete layer.12. The method recited in claim 1, wherein the surface concrete mixtureis poured over the base concrete layer within eight hours after formingthe base concrete layer.
 13. The method recited in claim 1, wherein thelarge aggregate has a mean diameter size of greater than three-eighthsof one inch and the small aggregate has a mean diameter of less thanthree-eighths of one inch.
 14. The method recited in claim 1, whereinthe surface concrete mixture is formed independent of large aggregate.15. A method of forming architectural concrete, the method comprisingthe steps of: pouring a base concrete mixture to define a base concretelayer, the base concrete mixture including large aggregate having a meandiameter size of greater than three-eighths of one inch; preparing asurface concrete mixture including small aggregate and sand, the smallaggregate having a mean diameter size of less than three-eighths of oneinch, the small aggregate and sand being mixed to define a prescribedcolor, the surface concrete mixture being formed independent of largeaggregate; and pouring the surface concrete mixture over the baseconcrete layer to define a surface layer.
 16. The method recited inclaim 15, wherein the surface concrete mixture is poured over the baseconcrete layer while the base concrete mixture is in an unhydratedstate.
 17. The method recited in claim 15, wherein the surface concretemixture is poured over the base concrete layer within eight hours afterforming the base concrete layer.
 18. An architectural concrete structurecomprising: a base concrete layer formed from a base concrete mixtureincluding large aggregate, the base concrete layer defining a basesurface; a surface layer formed on the base surface, the surface layerincluding small aggregate and sand, the small aggregate being smallerthan the large aggregate in the base concrete mixture, the smallaggregate and sand being mixed to define a prescribed color; and thesurface layer being formed on the base surface while the base concretemixture is in an unhydrated state to allow the surface layer to bond tothe base concrete layer independent of a cold joint therebetween. 19.The architectural concrete structure recited in claim 18, furthercomprising rebar disposed within the base concrete layer.
 20. Thearchitectural concrete structure recited in claim 18, wherein the largeaggregate has a mean diameter size of greater than three-eighths of oneinch and the small aggregate has a mean diameter of less thanthree-eighths of one inch.